This invention relates generally to inductive type and magnetoresistive type thin film magnetic heads, and more particularly to connection between a conductor film terminal and a flexible printed circuit board. Here, the term "conductor film terminal" means an external connection terminal for applying a current to a thin film magnetic head and inputting an input signal or outputting an output signal, made of a conductor film.
A thin film magnetic film consists of a head element fabricated by use of thin film processing technique such as sputtering, vacuum deposition, photoetching, and so forth. Particularly because delicate machining is possible, the thin film magnetic head can accomplish high density packaging and can realize a magnetic head having a small track width. The inductive type thin film magnetic head is produced by forming a lower thin magnetic film of permalloy (high permeability Ni-Fe alloy such as Ni-25%Fe alloy) or the like on a non-magnetic substrate such as glass by plating or vacuum deposition, forming then a conductor film having a predetermined pattern in such a manner as to cover the lower thin magnetic film, forming an upper thin magnetic film on the conductor film through an insulating film and extending the conductor film on the thin magnetic film head substrate for external connection.
Accordingly, the terminal width of the conductor film becomes very small as the track width becomes small. When the substrate of the thin film magnetic head is made of a magnetic material such as ferrite and is used also as the lower thin magnetic film, the terminal width of the conductor film becomes very small, too, with miniaturization of the track width. On the other hand, a thin film magnetic head of a magnetoresistive type which is used for reproduction only employs a magnetoresistive element, but the terminal width of the conductor film becomes likewise very small with the increase in the number of tracks. It is therefore necessary to improve the pitch accuracy between the terminals of adjacent tracks due to external connection. Moreover, a connection structure is necessary for external connection at the terminal of the conductor film which does not exert adverse influences on the thin film formation portion.
Hereinafter, a prior art example will be explained. Generally, the conductor film terminals 3 for external connection are formed on the surface of the magnetoresistive element 4 on the non-magnetic substrate 2', as shown in FIG. 4 and these conductor film terminals 3 are connected to a large number of lead terminals 7 exposed at one of the ends of the flexible printed circuit board 6 by a wire 12 made of Au, Al or the like. A connection method which connects both ends of wire to the counter-part is employed for this connection in accordance with wire bonding technique or the like. However, since connection is made at both ends of the Al or Au wire 12 and between a large number of terminals, bonding connection is necessary at a large number of spots. Incidentally, reference numeral 1 in FIG. 4 represents the thin film magnetic head and 5 does the insulating film.
The head described in another prior art reference, i.e. Japanese Patent Laid Open No. 172106/1984, will be explained. FIG. 5 of the accompanying drawings shows the main structural portion of the multi-channel thin film magnetic head 1 of this prior art. The magnetoresistive element 4 made of Fe-Ni alloy or Ni-Cr alloy is formed on the non-magnetic substrate 2' and the conductor film terminal 3 for connection with the flexible printed circuit board 6 is formed on the magnetoresistive element 4. The lead terminal 7 of the flexible printed circuit board 6 consisting partly of a transparent member 8' has Sn-Pb alloy 9' put thereto. After the lead terminal 7 is located to the conductor film terminal 3, laser beam is radiated through a glass sheet 13 to fuse the Sn-Pb alloy 9' so that a large number of connection spots between the lead terminal 7 of the flexible printed circuited board 6 and the conductor film terminal 3 can be connected exclusively by a reflow soldering method. Incidentally, reference numeral 10 in FIG. 5 represents a base film and 5 represents the insulating film.
The structure of the prior art techniques described above wherein the flexible printed circuit board and the conductor film of the thin film head are connected at both ends of the Al or Au wire involves the problem that since the number of connection points is great, workability is low and the number of manhour increases. The other prior art reference described above, i.e. Japanese Patent Publication No. 172106/1984, requires essentially the structure wherein the upper part of the lead terminal of the flexible printed circuit board is composed of the transparent material in order to fuse the solder of the lead terminal by use of the laser beam. Therefore, this technique is not suitable for the flexible printed circuit board having an opaque portion and imposes a structural limitation to the flexible printed circuit board. In order to fuse the solder, the connection portion must be heated to a high temperature near 300.degree. C. and not only the conductor film at the connection corresponding portion but also the thin film head structure itself must have heat resistance to this temperature. Accordingly, the structure of the thin film head element is limited by the problem of connection. Moreover, accuracy of pitch cannot be kept at the time of high density packaging due to non-uniformity of the thickness of the Sn-Pb alloy layer on the lead terminal of the flexible printed circuit board or due to the thermal deformation of the film on the reverse of the lead terminal of the flexible printed circuit board, and adjacent terminals are likely to come into contact with one another.